[Back]

C. Schattauer, L. Linhart, T. Fabian, T. Jawecki, W. Auzinger, F. Libisch:
"Graphene quantum dot states near defects";
Physical Review B, 102 (2020), 155430; 1 - 9.

Smooth confined graphene quantum dots (GQDs) localize Dirac electrons
with conserved spin and valley degrees of freedom. Recent experimental realization
of such structures using a combination of magnetic fields and a scanning
tunneling microscope tip showcased their potential in locally probing and
adjusting the valley degree of freedom. The present work models the influence
of lattice defects on the level structures of GQDs. We study both the adiabatic level
spacing "landscape" - orbital splitting and valley splitting - as well as
transition dynamics between GQD-states. The system is modeled using a tight-binding
approach with onsite- and hopping parameters in the vicinity of the defect region
extracted from density functional theory via Wanner orbitals while time propagation
is done using Magnus operators. Different defect types, such as double vacancy,
Stone-Walse, flower and Si substitution are considered. We predict tunable
valley splittings of the order of 2-20meV. The level structure can thus be
tailored at will by engineering appropriate defect geometries.

http://dx.doi.org/10.1103/PhysRevB.102.155430